The present invention relates to manufacture a pipe body by performing a bending operation on a metal plate.
Conventionally, there is disclosed a technique by which a pipe body, for example, a prism pipe body is made by bending a metal plate, such as in Japanese Patent Laid-Open No. Hei 11-290940.
In Japanese Patent Laid-Open No. Hei 11-290940, a prism pipe body is manufactured by using a rectangular metal plate as a material by means of pressing.
The method of manufacturing prism pipe body includes a first bending step, a second bending step, and a re-striking step. In the first bending step, a primary intermediate product is formed of a metal plate. In the second bending step, the primary intermediate product is processed to form a secondary intermediate product. In the re-striking step, the secondary intermediate product is processed to form a prism pipe body as a final product.
In the first bending step, both width direction sides of the metal plate are bent at the right angle in length direction. Accordingly, the primary intermediate product which includes flanges and a bottom plate is formed. The flanges face to each other. The bottom plate connects the flanges to each other.
In the second bending step, a concave surface having a predetermined width is formed on the bottom plate of the primary intermediate product lengthwise, and at the same time, both ends of the concave surface is bent at the right angle to inside. Accordingly, the second intermediate product is formed. The secondary intermediate product includes a pair of side walls which facing to each other. The cross section of the secondary intermediate product is U shape.
In the re-striking step, edges of a pair of flanges (seam) are contacted together by pressing a pair of side walls of the secondary intermediate product inside. Accordingly, a prism pipe body as a final product is formed.
According to this method of manufacturing the prism pipe body, the concave surface which is formed on bottom plate of secondary intermediate product, has a function to restrict a spring back force generated by pressing the pair of side walls together to inside. Accordingly a prism pipe body with square cross section, in which edges of the flanges closely contact together, can be manufactured only by pressing without welding edges of the flanges.
However, in this conventional method of manufacturing prism pipe body, even though the concave surface of secondary intermediate product has a function to restrict spring back force, spring back force which tends to open to outside still remains at the pair of side walls. Accordingly, it is difficult to stably manufacture without deflection the prism pipe body whose edges of flange (wall including the seam) closely contacts for mass production.
When testing a prism pipe body manufactured by the conventional working method, if edges of flanges are contacted each other or not, some are closely contacted each other, but many of them have gaps in the seam due to the spring back force appearing at the pair of side walls.
It is an object of the present invention to solve the above mentioned problems and to provide an method of manufacturing pipe body and pipe body manufactured by the method having capability of manufacturing pipe body stably without deflection in which a seam tightly contacted by pressing when mass production the pipe body.
In order to achieve the above objects, according to one aspect of the present invention, a method of manufacturing a metal pipe body by bending a flat metal plate at predetermined angles, comprising the steps of bending a portion near at least one end of the plate along an axis of the completed metal pipe body so as to have a predetermined angle of a corner of the completed metal pipe body; bending the same side as said bent portion of said metal plate at points which correspond to some integer times of one side of the completed metal pipe body in the same bending direction as said bent portion along the axis of completed metal pipe with an angle more than said predetermined angle; making one of the portion made by said second bending, concave toward the center of completed metal pipe body; pressing portions including edges of the plate towards the center of completed metal pipe body along the bottom surface of said portions including edges so as for said edges to get close contact and at the same time modifying said angles more than the predetermined angle into said predetermined angle; generating a modifying operation of said concave portion into convex form toward outside against center of the completed metal pipe accompanied with said angle modifying operation; accumulating inner stress for said concave portions tending back to said convex form through said modifying operation by making said concave portion flat thereby making a close contacting operation of said portion including edges by operation for all sides other than said convex portion and portions including edges enforcing towards the center of completed metal pipe; and maintaining said edges contacting together and said originally concave portion flat, is provided.
According to another aspect of the present invention, a method of manufacturing a metal pipe body by bending a flat metal plate at an angle, comprising the steps of bending a portion of the flat metal plate near at least one end of the flat metal plate along an axis of the completed metal pipe body so as to have a predetermined angle of a corner of the completed metal pipe body; bending the same side as said bent portion of said metal plate at points which correspond to some integer times of one side of the completed metal pipe body in the same bending direction as said bent portion along the axis to be completed metal pipe with an obtuse angle more than said predetermined angle; making one of the portion made by said second bending, concave toward the center portion of completed metal pipe body; pressing portions including edges of the plate towards center of the completed metal pipe body along the bottom surface of said portions including edges so as to get close contact of said edges and at the same time modifying said angles more than predetermined angle into said predetermined angle; modifying said concave portion into convex form toward outside against center of the completed metal pipe accompanied with said angle modifying operation; modifying said convex portion into flat by pressing said bottom surface and the surface facing to said surface with convex form towards center of completed metal pipe body with said portions including edges contacting together; accumulating inner stress for said concave portions tending back to said convex form through said modifying operation by making said concave portions flat thereby making close contacting operation of said portions including edges; and maintaining said edges contacting together and said originally concave portion flat, is provided.
According to other aspect of the present invention, a method of manufacturing pipe body having a seam and circular shaped cross section made of a rectangular metal plate, comprising the steps of: by bending said metal plate, forming a curved pipe-like intermediate product of oval-like cross section in which a pair of edges of said metal plate to be a seam of said pipe is still not contacted and located at one end of longer axis of said oval and extending along the axis of the completed pipe; and modifying the curved intermediate product by applying a force along the longer axis of said oval so as to force said edges contacted tightly with spring back force tending to return to the original oval shape, is provided.
According to still other aspect of the present invention, a method for manufacturing pipe body having a seam and polygonal cross section made of a rectangular metal plate, comprising the steps of: by bending said plate at plurality of points along its edge direction, forming a pipe-like intermediate product in which a pair of edges of said metal plate to be a seam of said pipe are still not contacted together and both and angles of one specified wall are greater than the predetermined value for angle of the completed pipe; making said pair of edges close contact by forcing said one specified wall convex to outside; and modifying convex said one specified wall flat so as to force said edges contacted tightly with spring back force tending to return to the convex shape, is provided.
The above stated methods makes possible to manufacture either a prism or cylindrical pipe body made of metal plate with the polygonal or circular cross section in which the seam of plate edges is closely contacted by aggressively utilizing a force which the convex and concave surface tend to return to the original shapes.
According to still other aspect of the present invention, a method for manufacturing pipe body having a seam and polygonal cross section made of a rectangular metal plate, comprising the steps of: a first processing step of forming a seam including wall by standing at least one portion of a pair of edges of said metal plate along its edge direction; a second processing step of forming remaining walls other than said seam including wall and making a pipe-like intermediate product in which a pair of edges of said metal plate to be a seam of said pipe are still not contacted and both end angles of one specified wall are greater than the predetermined value for angle of the completed pipe; a third processing step of making said pair of edges close contact by forcing said one specified wall convex to outside; and a fourth processing step of modifying convex said one specified wall flat so as to force said edges contacted rightly with spring back force tending to return to the convex shape, is provided.
The method makes it possible that a primary intermediate product having a wall including seam is formed at the first processing step, and a secondary intermediate product having remaining walls other than the wall including seam is formed at the second processing step, and by using the secondary intermediate product, pipe bodies having various shapes are formed.
According to still other aspect of the present invention, a pipe body having a seam and polygonal cross section made of rectangular metal plate, characterized by: being made through a pipe-like intermediate product prepared by bending said plate at plurality of points along its edge direction, in which a pair of edges of said metal plate to be a seam of said pipe is still not contacted and both end angles of one specified wall are greater than the predetermined value for angle of the completed pipe; and said pair of edges are closely contacted by forcing said one specified wall convex to outside and convex said one specified wall are flat so as to force said edges contacted tightly with spring back force tending to return to the convex shape, is provided.
By the above stated pipe body according to present invention, it is possible to make the seam closely contacted together without welding.
The seam may be located at the center of the wall including seam. And, the seam may be located between the wall including seam and adjoining wall. Further, the seam may be located at the center of three walls.
Moreover, according to the method, it is possible to manufacture a pipe body whose shape of cross section is triangle, pentagonal, hexagon, or octagon shape.
Preferably, the one specified wall comprises a flat portion and a curved portion. When the curved portion is formed between the adjoining wall and the flat portion and the curved convex surface is modified to be flat, flatness of it can be ensured.
In the method of manufacturing pipe body, it is more preferable to use the pipe body having a cross section of a rectangle shape, and it is also preferable that an angle between the one specified wall and the adjoining wall of the intermediate product is an obtuse angle when forming a curved convex surface.
When the cross section of the pipe body is rectangular, it is preferable that defining each of the walls of the pipe body as a bottom wall, a pair of side walls adjacent to the bottom wall and a upper wall facing to the bottom wall, and the seam is formed on the upper wall.
Preferably, the metal plate includes engaging concave portion such as tapped holes or notch for installation previously formed on the wall in order to use the pipe body as a supporting member for, image forming apparatus, such as copy machine, for example, without further work after assembling.
Preferably, a forming process of the pipe body is performed under consideration of extension when bending the metal plate.
According to still other aspect of the present invention, a pipe body having a seam and circular cross section made of rectangular metal plate, characterized by: being made through a curved pipe-like intermediate product of oval-like cross section made by bending said metal plate in which a pair of edges of said metal plate to be a seam of said pipe is still not contacted and located at one end of longer axis of said oval and extending along the axis of the completed pipe; and formed by modifying the curved intermediate product by applying a force along the longer axis of said oval so as to force said edges contacted tightly with spring back force tending to return to the original oval shape, is provided.
According to still other aspect of the present invention, a pipe body having a seam and polygonal cross section made of a rectangular metal plate, characterized by: being made through a pipe-like intermediate product prepared by bending said plate at plurality of points along its edge direction, in which a pair of edges of said metal plate to be a seam of said pipe are still not contacted together and both end angles of one specified wall are greater than the predetermined value for angle of the completed pipe; said pair of edges are closely contacted by forcing said one specified wall convex to outside; and convex said one specified wall is modified flat so as to force said edges contacted together tightly with spring back force tending to return to the convex shape, is provided.
According to the above described pipe body, it is possible to closely contact the seam together without welding.
According to still other aspect of the present invention, a prism pipe body having a seam extending along axis direction of said pipe body made of a rectangular metal plate, characterized by pair of edges of said plate consisting said seam are closely contacted by spring back force and having a fastening plate formed on a surface to be tied with other materials, is provided.
According to still other aspect of the present invention, a prism pipe body made of a rectangular metal plate, comprising a bottom wall, a pair of adjoining walls to said bottom wall and upper walls one of which includes a seam confronting with said bottom wall, wherein: said seam is closely contacted by spring back force; said walls are extending along the direction of axis of the pipe body; and a fastening plate is formed on a surface to be tied with other materials, is provided.
In the above described pipe bodies, because the fastening plate is formed integrally, fastening strength can be improved more than any prism pipe bodies of prior art fastened with other materials using a bracket.
According to still other aspect of the present invention, a prism pipe body made of a rectangular metal plate, comprising a bottom wall, a pair of adjoining walls to said bottom wall and upper walls including seam which is confronting with said bottom wall, characterized by a first residual stress distortion appeared at corners portion between said pair of adjoining walls and said bottom wall which makes said seam open, a second residual stress distortion appeared at center portion of said bottom wall induced by plastic deformation which has counter direction of said first residual distortion, wherein said seam is closely contacted by said second residual stress distortion which makes said bottom wall convex to outside, and an area exists between said corner and said center of bottom wall which has a low residual stress distortion, is provided.
According to still other aspect of the present invention, a prism pipe body characterized by: being made through a pipe-like intermediate product comprising one specified wall, a pair of side walls adjoining to said specified wall and other walls, wherein: the angles between said specified wall and said a adjoining walls are obtuse, and said specified wall concave into inside; a stress distortion toward inside generated on said intermediate product through making said specified wall convex to outside by deforming said pair of walls of said intermediate product toward inside; forcing the angle between said specified wall and said pair of walls square by making plastic distortion so as for said specified wall to be deformed flat with making center portion of said specified wall as fulcrum, through forcing top wall including seam which is confronted to said bottom wall with restricting said pair of walls and making said intermediate product completed pipe body of which bottom wall corresponds to said specified wall and a pair of side walls adjoining said bottom wall correspond to said pair of side walls; wherein said bottom wall deforms convex to outside by a residual stress distortion generated at center of said specified wall which has counter direction of another residual stress distortion generated at corners between said pair of adjoining walls and said bottom wall making said seam open; said seam is closely contacted by said another residual stress distortion; and an area exists between said corner and said center of bottom wall having a low residual stress distortion, is provided.